Heat-treatable platinum-gallium-palladium alloy for jewelry

Abstract

A method of making jewelry comprising formulating a platinum alloy of at least 95 weight percent platinum, 1 to 5 weight gallium and palladium in an amount of less than about 3 weight percent, heat treating this alloy to increase the Vickers hardness by at least 20% but to not greater than a Vickers hardness of 350.

What is claimed is:  
     
       1. A method for making jewelry, which comprises: 
       formulating a platinum alloy of at least about 95 weight percent platinum, about 1 to 5 weight percent gallium, and an additional alloying element of palladium in an amount effective as a property enhancing agent but less than about 3 weight percent, said alloy having an initial Vickers hardness;  
       heat-treating the alloy to increase the Vickers hardness by at least about 20% but to not greater than a Vickers hardness of 350; and  
       utilizing the heat-treated alloy as a component of jewelry.  
     
     
       2. The method of  claim 1  wherein the heat-treating operation comprises solution-treating the alloy at a temperature of at least about 1700 F.; quenching the solution-treated alloy to a temperature of below about 200 F.; and hardening the quenched alloy at at least 900 F. for a sufficient time to achieve the desired hardness. 
     
     
       3. The method of  claim 2  wherein the solution treating temperature is at least 1800 F., the alloy is held at that temperature for at least 10 minutes, the solution-treating step is an annealing step conducted in an inert, non- or anti-oxidizing environment, and the annealed alloy is quenched in water. 
     
     
       4. The method of  claim 2  wherein the hardening heat-treatment is conducted by heating the alloy in an inert, non- or anti-oxidizing gas atmosphere for at least 30 minutes at about 1100 to 1200 F. 
     
     
       5. The method of  claim 4  wherein the hardened alloy is cooled to room temperature. 
     
     
       6. The method of  claim 1  wherein palladium content is between 0.5 and 2.5 weight percent, the initial Vickers hardness is between 125 and 200 and the final Vickers hardness is between 150 and 300. 
     
     
       7. The method of  claim 1  further comprising adding one or more property enhancing elements to the alloy in a total amount of no more than 2 percent.